This invention relates to catalytic processes for preparing vinyl aromatic compounds and to metal complexes used as catalysts in such processes.
Many processes for making vinyl aromatic compounds are known. Most, however, require two or more chemical steps from the aromatic starting material. For example, styrene may be produced in two steps by the alkylation of benzene to ethylbenzene, and the dehydrogenation of ethylbenzene to styrene. See, for example, Lewis, P. J.; Hagopian, C.: Koch, P.: Kirk-Othmer Encyclopedia of Chemical Technology, Third Ed., Vol. 21, p. 770, John Wiley & Sons (1983).
Several processes are known which require only one step from the olefin and aromatic compound to the corresponding styrenics. Kozhevnikov, 1. V. and Matveev, K. I., "On the Mechanism of Arylation of Ethylene by Palladium", Reaction Kinetics and Catalysis Letters, Vol. 5, No. 1, 61-65 (1976) discloses a process for phenylating ethylene with benzene in the presence of palladium acetate. Hong, P., and Yamazaki, H., "Rhodium Carbonyl-Catalyzed Activation of Carbon-Hydrogen Bonds for Application in Organic Synthesis. V. Phenylation of Olefins with Benzenes," Journal of Molecular Catalysis, Vol. 26, p. 297 (1984) discloses a process for the reaction of ethylene with benzene under carbon monoxide pressure in the presence of a rhodium carbonyl catalyst. Shimuzu, K. and Ohta, N., Chemical Abstracts AN #CA89(12):90442k (1978) discloses a process for producing styrenes in one step from the olefin and aromatic compound using heterogeneous rhodium or iridium catalysts on inorganic supports. In view of the foregoing, it would be desirable to produce a one-step process for the production of vinyl aromatic compounds which is more selective than the one-step processes of the prior art.